Extruded modular panel units of the type of the present invention are known, for example, from the U.S. Pat. Nos. 4,573,300, 4,998,395 and 5,348,790, the teachings of which are incorporated herein by reference.
In all of these patents, there are disclosed panel units having two interconnected, spaced-apart major surfaces and a joining flange at each of its ends, both flanges projecting at the same direction from a single major surface of the panel.
While such panels have been used to advantage for many years, it has been found that in some instances under adverse weather conditions, difficulties may be created with respect to waterproofing and withstanding strong winds, especially with a structure composed of two parallel disposed panel units interconnected by H-shaped connectors.